CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings (Accumulated Deficit)
Beginning balance (in shares) at Dec. 31, 2019		30,555,677
Beginning balance at Dec. 31, 2019	$ 389,877	$ 306	$ 758,853	$ (4,467)	$ (364,815)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under stock compensation plan, net of forfeitures (in shares)		1,164,797
Issuance of common stock under stock compensation plan, net of forfeitures	0	$ 11	(11)
Stock-based compensation expense	7,717		7,717
Vesting of restricted stock (in shares)		(149,548)
Vesting of restricted stock	(158)	$ (1)	(157)
Other comprehensive income (loss)	(264)			(264)
Net loss	(343,573)				(343,573)
Ending balance (in shares) at Sep. 30, 2020		31,570,926
Ending balance at Sep. 30, 2020	53,599	$ 316	766,402	(4,731)	(708,388)
Beginning balance (in shares) at Jun. 30, 2020		31,652,635
Beginning balance at Jun. 30, 2020	69,950	$ 317	764,382	(4,863)	(689,886)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under stock compensation plan, net of forfeitures (in shares)		(80,882)
Issuance of common stock under stock compensation plan, net of forfeitures	0	$ (1)	1
Stock-based compensation expense	2,020		2,020
Vesting of restricted stock (in shares)		(827)
Vesting of restricted stock	(1)		(1)
Other comprehensive income (loss)	132			132
Net loss	(18,502)				(18,502)
Ending balance (in shares) at Sep. 30, 2020		31,570,926
Ending balance at Sep. 30, 2020	53,599	$ 316	766,402	(4,731)	(708,388)
Beginning balance (in shares) at Dec. 31, 2020		31,557,809
Beginning balance at Dec. 31, 2020	20,409	$ 316	768,429	(4,501)	(743,835)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under stock compensation plan, net of forfeitures (in shares)		1,471,150
Issuance of common stock under stock compensation plan, net of forfeitures	0	$ 14	(14)
Stock-based compensation expense	4,191		4,191
Vesting of restricted stock (in shares)		(188,875)
Vesting of restricted stock	(473)	$ (2)	(471)
Other comprehensive income (loss)	(32)			(32)
Net loss	(48,827)				(48,827)
Ending balance (in shares) at Sep. 30, 2021		32,840,084
Ending balance at Sep. 30, 2021	(24,732)	$ 328	772,135	(4,533)	(792,662)
Beginning balance (in shares) at Jun. 30, 2021		31,350,677
Beginning balance at Jun. 30, 2021	(9,731)	$ 314	770,997	(4,431)	(776,611)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under stock compensation plan, net of forfeitures (in shares)		1,490,234
Issuance of common stock under stock compensation plan, net of forfeitures	0	$ 14	(14)
Stock-based compensation expense	1,153		1,153
Vesting of restricted stock (in shares)		(827)
Vesting of restricted stock	(1)	$ 0	(1)
Other comprehensive income (loss)	(102)			(102)
Net loss	(16,051)				(16,051)
Ending balance (in shares) at Sep. 30, 2021		32,840,084
Ending balance at Sep. 30, 2021	$ (24,732)	$ 328	$ 772,135	$ (4,533)	$ (792,662)